The present invention relates to a method for providing a tube of thermoplastic material with a thickened end by subjecting a tube end, which has been brought into a deformable state by applying heat, to an upsetting action.
Such a method is known per se. According to this known method, during the extrusion of a tube the discharge rate of the tube is reduced such that, in a part thereof, a greater wall thickness is produced. This part of the tube with thickened wall is thereupon, by a separate operation, provided with a socket end and a groove, if desired. The formation of the tube part with thickened wall during extrusion is, however, attended with the drawback that it is impossible to obtain a wall thickening which meets well-defined conditions.